| Compared with conventional flight vehicles,morphing aircraft can change the geometry of wing or body for higher efficiency or maneuver capability under different flight conditions.In recent years,along with the advance of material science and manufacturing technology,foreign researchers have proposed many kinds of static morphing aircraft configuration;some key technologies were thoroughly studied and some solutions were tested experimentally,with excellent performance demonstrated.The morphing aircraft research in China is still premature,limited to theoretical studies and ground testing,far from practical applications.In addition,existing studies mainly focus on static morphing,and dynamic morphing is rarely studied.In this paper,history and current situation of morphing flight vehicles home and abroad are analyzed and summarized based on morphing methods and configurations,with key technologies required analyzed.Morphing structure and flexible skin structure are studied by taking aerodynamic efficiency and maximum aerodynamic force as goals based on research on the aerodynamic mechanism of airfoil morphing.The feasibility of morphing is demonstrated and simulation and experiment are carried out for the comprehensive performance of the morphing flight vehicle.Main contents and achievements of this studies are shown as follows:1.A airfoil camber morphing model which is capable of morphing both trailing edge and leading edge by using variable parameters is proposed,with the lift and drag performance in steady flow field analyzed through CFD simulations;CFD simulations for the dynamic rotation model of the 2d single blade under in unsteady flow field is carried out to study generation,scale and efficiency of aerodynamic forces of the model,in the meantime,the aerodynamic performance of a rigid blade and a flexible cambering blade is studied with comparison made;a model for 2d chord-wise motion of a flapping wing is developed to study the influence of cambering airfoil on aerodynamic performance.2.Targeting cyclodial propeller and flexible flapping wing,the aerodynamic performance of flight vehicles with 3d flexible dynamic morphing wing is studied.Emphasis is laid on the interaction between blades of cyclodial propeller,and the research results show that for both rigid and flexible blades,both the aerodynamic force and efficiency of a single blade decrease with the increase of the number of blades.The aerodynamic interference between flexible cambering blades is slightly larger than that of rigid blades,but it has relatively higher aerodynamic efficiency.A flexible flapping wing model with large morphing capability is proposed,and the aerodynamic performance of both rigid and flexible wings is studied through comparison by taking propulsion and aerodynamic performance as main objectives.3.Based on nondimensionalization of parameters of the supporting structures(trapezoid,Ushaped,V-shaped)of three kinds of flexible skins and the analysis of their mechanical model,their inplane elastic characteristics are compared through numerical simulation and mechanical experimental;the out-plane characteristics of the three flexible skin structures are studied through numerical simulation and experimental verification,the out-plane bearing capability after tensile deformation is also studied.4.Based on supporting structure with flexible skin,a variable camber wing section with both leading and trailing edges that can be rotated for fixed wing aircraft is designed to replace conventional surfaces for attitude control.Compared with wings using conventional flaps and ailerons,this morphing wing can obviously shorten the distances for takeoff and landing.Based on conventional cycloidial propellers,cambering flexible blade and corresponding driving mechanism,which can be used to control aerodynamic vectors,are designed and manufactured,and experiment results show that the aerodynamic efficiency of cycloidial propellers can be improved by about 6-8% by adoption of flexible blades. |
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